What Is Presbyopia?

The definition of presbyopia according to the Merriam-Webster dictionary is “a visual condition which becomes apparent especially in middle age and in which loss of elasticity of the lens of the eye causes defective accommodation and inability to focus sharply for near vision.”¹ Aside from the medical definition, presbyopia can have a very different meaning to each patient that we see in the clinic every day.

It is well known that people of today are living longer. The average life expectancy worldwide is 73.2 years old.² As the population becomes older, there are many different aging changes that occur. One of the most important, yet most challenging, age-related changes that we encounter as optometrists occurs in the crystalline lens. From requiring the dreaded “bifocals” or having to take glasses off to read the newspaper, every patient has different visual needs. This presents an interesting challenge as the population continues to age and develops increasing visual demands.

Classification of Presbyopia

Time and time again, we hear the same story. A 40-year-old new patient presents to your office because everything seems blurrier at near, or they feel like their arms are not long enough to read anymore. Starting in their early-to-mid 40s, many patients will begin to experience these exact symptoms.³ The onset of presbyopia is the first stage in dysfunctional lens syndrome. These changes involve the lens becoming harder and less elastic with age. Mechanical compression tests have confirmed that the lens itself has a substantial increase in rigidity as patients progress toward presbyopia.⁴ These lens changes eventually progress toward the development of cataracts, in turn requiring cataract extraction.

There was not a widely accepted formal consensus to classify the different stages of presbyopia⁵ until a recent article published in 2022 established a presbyopia classification system. The authors determined that mild presbyopia required +1.25D of add power, moderate presbyopia required between +1.25D and +2.00D add power, and advanced presbyopia required >+2.00D of add power.⁶

Accommodation also begins to decrease as the lens loses elasticity. Around the fifth decade of life, accommodative amplitude declines to the point where the near point of the eye is now farther away than the reading distance. Accommodation decreases to essentially 0D by the age of 60.⁷ At this time, patients are considered absolute presbyopes.

Prevalence

Data released in April 2022 by the United Nations estimated that there are 7.9 billion people living in the world.⁸ In 2015, it was determined that approximately 1.8 billion people were presbyopic,⁹ and this was estimated to reach 2.1 billion by 2020.¹⁰ Accordingly, 26% of the world’s population is currently presbyopic. The prevalence of presbyopia in the United States ranges from 83.0% to 88.9% for adults aged 45 years old and older,¹¹ and there was an estimated total of 123 million presbyopes in the country in 2020.

Of these 1.8 billion presbyopes worldwide, an estimated 826 million have near visual impairment due to a lack of, or inadequate, near vision correction.⁸ People living in high-income countries are more likely to have access to near vision correction based on health expenditure and access, as opposed to those residing in lower-income countries. The greatest burden of vision impairment from uncorrected presbyopia therefore occurs in developing, low-resource countries, where up to 94% of the population may be under- or uncorrected.¹² The global unmet need for presbyopia correction was approximated to be 45% in 2015.⁹ For comparison, near vision correction rates ranged from 96% in Europe to only 6% in Africa.¹²

Impact on Quality of Life

Multiple studies have shown that patients in both high-income and low-income countries suffer decreased quality-of-life scores due to presbyopia.^11,13 One study showed that 22% of presbyopic patients reported a decrease in quality-of-life score. Uncorrected presbyopia caused two-fold increased difficulty in performance of near-vision-related tasks and eight-fold greater difficulty in very demanding near-vision-related tasks, with 80% of these patients reporting troubles with performing near-vision activities.¹¹ Further, 12% of presbyopic patients needed help in performing routine tasks, which in turn led to distress and decreased self-esteem.¹¹ One cross-sectional study involving American presbyopes corrected with glasses showed that they experienced a decrease in quality of life similar to those with treated hypertension.¹⁴ Maxwell et al compared multifocal intraocular lenses (IOLs) with conventional monofocal IOLs and found that 80% of patients were willing to pay $5 per day to be spectacle independent.¹⁵

The concept of presbyopia involves a psychological component as some patients perceive bifocal glasses to be unattractive or a sign of old age.¹⁴ The average presbyope today may live an active lifestyle, in which wearing glasses may impede their performance of activities. The increased use of digital devices and the rise in near work further accentuate presbyopic demands and contribute to this psychological impact.

Economic Impacts

One study looking at the global burden of productivity loss due to uncorrected presbyopia found that, among individuals aged 50 and younger, there was an associated potential productivity loss of $11 billion. In those aged 65 and younger who were untreated presbyopes, the potential productivity loss was estimated at $25.4 billion if all were assumed to be productive.^11,12 The authors found that correcting presbyopia, like the 96% of presbyopes in Europe, would decrease the burden to $1.4 billion.¹²

Treatments

When treating presbyopia, the first-line therapy was routinely progressive addition lenses or bifocal lenses. Since presbyopic patients, now more than ever, seek independence from having to wear glasses, there are multiple therapies that may allow patients to achieve this goal. Some of these choices include multifocal IOLs, multifocal contact lenses, refractive lens exchange (RLE), the FDA-approved light adjustable lens (LAL) by RxSIGHT, and the latest, an FDA-approved pharmaceutical drop, Vuity (1.25% pilocarpine ophthalmic solution, Allergan/Abbvie).

• Multifocal IOLs: These IOLs were developed to improve near vision outcomes after cataract surgery. They work by dividing light into different focuses, which change vision due to the dispersion that occurs when light enters the eye.¹⁶ There are various designs that work by refraction, diffraction, or a combination of both designs.
• Multifocal contact lenses: These lenses offer a modality that most practitioners are familiar with and includes soft contact lenses, rigid gas permeable designs, and scleral lenses.
• Refractive lens exchange: In RLE, the crystalline lens is simply removed and exchanged for a multifocal IOL. This is often a better surgical option for older presbyopes since it removes the cataract and treats the loss of near vision.¹⁷
• Light adjustable lens: The LAL is a newer multifocal IOL that can be customized 2-4 weeks after cataract surgery. The customization is performed through a series of office-based light treatment procedures until the patient reaches his or her target refractive status.¹⁸
• Vuity: The first and only FDA-approved prescription eye drop for treating presbyopia, this drop is composed of pilocarpine hydrochloride ophthalmic solution 1.25%, dosed once per day in each eye.¹⁹

All Things Considered

Presbyopia is a highly prevalent ocular condition that has worldwide impacts involving healthcare costs, quality of life, and economic impacts. It is something that we, especially as optometrists, see everyday in clinical practice. The significant impact it can have on the livelihood of patients is, however, sometimes overlooked. We are fortunate to be living in a world with advances in technology, pharmaceuticals, surgery, and lens design, all of which can help us alleviate some of the burden caused by presbyopia. Helping patients cope with the loss of near vision is something that we are more than capable of achieving. Presbyopia will continue to affect our aging population for years to come, and these numbers highlight how important it is for us to effectively manage this patient population. ■

References

1. Presbyopia. Merriam-Webster website. Accessed April 21, 2022. https://www.merriam-webster.com/dictionary/presbyopia .
2. Life expectancy of the world population. Worldometer website. Accessed April 21, 2022. https://www.worldometers.info/demographics/life-expectancy/ .
3. Adult vision: 41 to 60 years of age. American Optometric Association website. Accessed April 21, 2022. https://www.aoa.org/healthy-eyes/eye-health-for-life/adult-vision-41-to-60-years-of-age?sso=y .
4. Glasser A. Presbyopia and aging in the crystalline lens. J Vis. 2010;3(12):22.
5. Patel I, West SK. Presbyopia: prevalence, impact, and interventions. Community Eye Health. 2007;20(63):40-41.
6. McDonald MB, Barnett M, Gaddie I, et al. Classification of presbyopia by severity. Ophthalmol Ther. 2022;11(1):1-11.
7. Pescosolido N, Barbato A, Giannotti R, et al. Kinetics of human lenses: prevention of the cataract. Int J Ophthalmol. 2016;9(10):1506-1517.
8. Current population. Worldometer website. Accessed April 2, 2022. https://www.worldometers.info/world-population
9. Fricke TR, Tahhan N, Resnikoff S, et al. Global prevalence of presbyopia and vision impairment from uncorrected presbyopia. Ophthalmology. 2018;125(10):1492-1499.
10. Understanding presbyopia’s symptoms, causes and treatments. Versant Health website. Accessed April 21, 2022. https://versanthealth.com/blog/understanding-presbyopias-symptoms-causes-and-treatments/ .
11. Berdahl J, Bala C, Dhariwal M, Lemp-Hull J, Thakker D, Jawla S. Patient and economic burden of presbyopia: a systematic literature review. Clin Ophthalmol. 2020;14:3439-3450.
12. Frick KD, Joy SM, Wilson DA, et al. The global burden of potential productivity loss from uncorrected presbyopia. Ophthalmology. 2015;122(80):1706-1710.
13. Goertz AD, Stewart WC, Burns WR, et al. Review of the impact of presbyopia on quality of life in the developing and developed world. Acta Ophthalmol. 2013;92(6):497-500.
14. Luo BP, Brown GC, Luo SC, et al. The quality of life associated with presbyopia. Am J Ophthalmol. 2008;145(4):618-622.
15. Maxwell WA, Waycaster CR, D’Souza AO, Meissner BL, Hileman K. A United States cost-benefit comparison of an apodized, diffractive, presbyopia-correcting, multifocal intraocular lens and a conventional monofocal lens. J Cataract Refract Surg. 2008;34(11):1855-1861.
16. Salerno LC, Tiveron MC Jr, Alió JL. Multifocal intraocular lenses: types, outcomes, complications and how to solve them. Taiwan J Ophthalmol. 2017;7(4):179-184.
17. Schallhorn SC, Schallhorn JM, Pelouskova M, et al. Refractive lens exchange in younger and older presbyopes: comparison of complication rates, 3 months clinical and patient-reported outcomes. Clin Ophthalmol. 2017;11:1569-1581.
18. About us. RxSight website. Accessed April 21, 2022. https://www.rxsight.com/us/about-us/ .
19. Vuity. Allergan website. Accessed April 21, 2022. https://www.vuity.com/ .

Dr. Patel obtained her Doctor of Optometry at the University of Waterloo School of Optometry and Vision Science. She is currently a Primary Care Resident at Northeastern State University Oklahoma College of Optometry specializing in ocular disease.

Dr. Petry is a graduate of Midwestern University Arizona College of Optometry, where she earned her Doctor of Optometry (O.D.) degree. She is currently completing a residency in Primary Care at Northeastern State University Oklahoma College of Optometry.

Dr. Lighthizer is an Associate Professor, Chief of Specialty Care Clinics and Director of Continuing Education at the NSU Oklahoma College of Optometry. He is a member of the editorial board of Presbyopia Physician.